Are there any built-in .NET alternatives for using power of a number (Math.Pow) without errors?

Question

Math.Pow seems to be not working correctly for big results. Probably that is because it uses double for calculations (How is Math.Pow() implemented in .NET Framework?).

For example:

public static void Main()
{
    Console.WriteLine((long)Math.Pow(17, 13));
    Console.WriteLine(Pow(17, 13));
}

public static long Pow(int num, int pow)
{
    long answer = 1;
    for (int i = 0; i < pow; i++)
    {
        answer *= num;
    }

    return answer;
}

The result from the above code is:

9904578032905936
9904578032905937

Are there any built-in .NET alternatives for using power of a number without errors?

You see rounding errors. Use `Math.Round()` if you expect an integer result. — DrKoch, Mar 07 '15 at 10:10

Douglas · Accepted Answer · 2015-03-07T10:16:00.937

The BigInteger structure has a Pow method. This structure resides in the System.Numerics namespace, and was introduced in .NET Framework 4.0. You need to add a reference to the System.Numerics assembly before using it.

using System;
using System.Numerics;

public static class Program
{
    public static void Main(string[] args)
    {
        Console.WriteLine(BigInteger.Pow(17, 13));   // 9904578032905937
    }
}

Note that BigInteger is only suitable for integer arithmetic; it cannot handle fractional numbers.

Are there any built-in .NET alternatives for using power of a number (Math.Pow) without errors?

1 Answers1